Preparation of the Nanocomposites (Nano ZnO/Multi Wall CNTs) by the Arc Discharge Method for Adsorbing (Fe3+) from Water Samples Contain FeCl3 Salt

The maximum limit for dissolved iron allowed to be in the drinking water is (0.3 mg/L). Ferric chloride is an important coagulant which used in drinking water treatment plants. The removal of residual Fe³⁺ is required after the treatment process. Therefore, the presented work studied the removal of Fe³⁺ from FeCl₃ aqueous solutions by using a novel nanocomposites (Nano ZnO/MWCNTs) which had been synthesized by the arc discharge method at (I_ac=15 A, 70 V and 25 °C) in deionized water. TEM, XRD, EDX and FTIR have confirmed the synthesizing success. The average nano size of Nano ZnO and outer diameter of MWCNTs were 15.68 and 18.03 nm, respectively. The optimum dose was (5.0 mg/100 mL) with shaking at 200 rpm in an alkaline medium for a contact time of 60 min. The Fe³⁺ concentration was reduced from 1.0120 to 0.1646 mg/L at (pH = 7.0) and from 4.020 to 0.9947 mg/L at (pH = 9.0) and from 6.060 to 0.6749 mg/L at (pH = 12.0). The high maximum adsorption capacity of Fe³⁺ on the surface of (Nano ZnO/MWCNTs) is 258.78 mg/g according to Langmuir isotherm model at (pH = 12.0). This adsorption is a multilayer physical process according to Freundlich isotherm model and an exothermic process according to Temkin isotherm model. Moreover, this adsorption obeys pseudo-first order kinetic model and Intra-particle diffusion kinetic model. Nano ZnO/MWCNTs is suitable for drinking water treatment from Fe³⁺ at pH = 7 and pH = 8. It can be used for polluted water treatment from Fe³⁺ before discharging it in to rivers or lakes at (pH = 9.0).

Graphical Abstract